package store

import (
	"bytes"
	"errors"
	"fmt"
	"os"
	"path/filepath"
)

func persistPrivateData(dir, name string, data []byte) error {
	if err := os.MkdirAll(dir, 0700); err != nil {
		return err
	}
	info, err := os.Lstat(dir)
	if err != nil || !info.IsDir() || info.Mode().Perm() != 0700 {
		return errors.New("private data directory must have mode 0700")
	}
	target := filepath.Join(dir, name)
	if info, err := os.Lstat(target); err == nil {
		if !info.Mode().IsRegular() || info.Mode().Perm() != 0600 {
			return errors.New("existing private data must be a regular 0600 file")
		}
		existing, err := os.ReadFile(target)
		if err != nil {
			return err
		}
		if !bytes.Equal(existing, data) {
			return errors.New("private original data conflicts with existing file")
		}
		f, err := os.Open(target)
		if err != nil {
			return err
		}
		if err := errors.Join(f.Sync(), f.Close()); err != nil {
			return err
		}
		return syncPrivateDirectory(dir)
	} else if !errors.Is(err, os.ErrNotExist) {
		return err
	}
	f, err := os.CreateTemp(dir, ".pending-")
	if err != nil {
		return err
	}
	temp := f.Name()
	defer os.Remove(temp)
	_, writeErr := f.Write(data)
	syncErr := f.Sync()
	closeErr := f.Close()
	if err := errors.Join(writeErr, syncErr, closeErr); err != nil {
		return fmt.Errorf("persist private original bytes: %w", err)
	}
	if err := os.Rename(temp, target); err != nil {
		return err
	}
	return syncPrivateDirectory(dir)
}
func syncPrivateDirectory(dir string) error {
	f, err := os.Open(dir)
	if err != nil {
		return err
	}
	return errors.Join(f.Sync(), f.Close())
}